devtools/mailer: move template to google storage bucket.
devtools/mailer: move template to google storage bucket.

Save the message template in a json file and parse it
before sending email

Change-Id: I1eb90496abfcb111925228e546cd1f7b85c953f4

vanadium/go.devtools,vanadium/go.devtools,vanadium/go.devtools